21 Nov 2014

Why You Don't Bite Your Tongue Every Time You Eat and Other Amazing Tongue Facts

by Jan Thornhill

Most, though not all, people can make a simple tongue roll. A few
can make multiple rolls. Four is called a "cloverleaf." (Wikipedia)


I went out for dinner with friends a couple of nights ago. Chinese dumplings. Yum! I was so hungry and was eating so fast that I chomped down on my own tongue. Hard. The cut was deep enough that I thought for a minute I might need stitches...except there were more dumplings to eat. Though it hurt like heck (tip: stop eating hot sauce or anything acidic for a day or two after biting your tongue!), I decided to leave it and see what happened. By the end of dinner it had stopped bleeding. By bedtime, the flap that I'd almost sheared off had sealed itself neatly back in place, and by the end of the following day it appeared to be completely healed. Amazing!

If you look under your tongue, you'll see how rich it is in
blood vessels it. (Miserlou - Wikipedia)
Our tongues, it turns out, heal faster than any other part of our bodies except our corneas. Unless you have a severe tongue injury, in which case you should visit the ER, your tongue is so rich in blood vessels that nutrients and oxygen and other repair factors are delivered with such speed that a small self-inflicted wound will completely heal in only a day or two.

Why We Don't Bite Our Tongues Every Day

Your tongue's primary job is to move solid food into position between your teeth to be chewed, and then to shift that wad of mashed food, properly called a bolus, toward your throat so you can swallow it. The amazing thing is how precise this complex action is. Though we are capable of consciously controlling how we chew, most of the time when we're eating we're not thinking about what our tongues and jaws are doing at all. So how do we, and other mammals, manage to avoid eating our own tongues? Well, science is making great strides in answering this question. New research with mice has now shown that, while eating, connections between premotor neurons that control jaw and tongue muscles are exquisitely coordinated, making it impossible to automatically close the mouth without the tongue being simultaneously retracted.  

As well as helping us to eat, the tongue is also adept at cleaning our teeth and helping us drink. It also works like a piston, allowing us to suck, which is a vitally important function for toothless babies: the tongue produces low pressure when it moves backwards with the mouth closed, which causes fluid to be sucked in. Next time you're having a drink using a straw, try to get some liquid in your mouth without moving your tongue—you'll see that it's impossible. 

Talking Tongues

Owen Price's 1665 illustration of human speech. 

Bet you can't say this three times fast: "The sixth sick sheik's sixth sheep's sick." New research is now offering an explanation for why tongue twisters like this twist our tongues (I think I just made up a new one!). 

When we speak, the brain acts like a symphony conductor, perfectly coordinating the complex movements of tongue, lips, jaw, and larynx to produce words. But how does it do it? Using electrodes on brain surgery patients, scientists have recently been able to pinpoint the specific locations of brain activity that coincide with the enunciation of various common English syllables. When these areas of the brain were mapped out, it was found that consonants and vowels are controlled quite differently, even when the sounds enunciated are produced in the same parts of the vocal tract. On top of that, the brain appears to coordinate the formation of words according to the muscles that need to move to produce them instead of by sound, as was previously thought. Front-of-the-mouth sounds, for instance, like "sss" and "shh," are clustered very closely together in the brain, which makes it much easier for our mouths to get confused when trying to produce these sounds in an overlapping series, hence our difficulty in repeating tongue twisters.

Stick Out Your Tongue!

Two pages from a treatise on the diagnostic value of the appearance
of the tongue by Mosai Tsuchida (1765-1837) (Wikipedia)

Have you ever wondered why your doctor asks you to stick out your tongue? Doctors can actually tell a lot about your health by looking at your tongue. In Western medicine, a darker or lighter than normal tongue can be a sign of serious medical issues, as can dark spots or patchiness. Practitioners of traditional Chinese medicine take the state of one's tongue even more seriously and believe that even subtle changes in the tongue's colour, coating, and shape can tell them so much about other parts of a patient's body that there are whole books devoted to the practice of tongue diagnostics. 

Fun Tongue Facts

Fountain in Pontevedra, Spain (Joseogon)
  • In many parts of the world, sticking your tongue out at someone is considered childish or rude behaviour. It is such an insult in Italy that in 2009 a man was fined almost $2,000 for sticking his tongue out at his neighbour! In Tibet, however, sticking one's tongue out is a friendly greeting. This practice began centuries ago as an offering of proof that someone is friendly, not an incarnation of Lang Darma, a cruel, black-tongued, 9th century king.
  • Proportionately, the human tongue is has the most powerful muscles in the body. The record weight lifted by a tongue is 12.5 kg by Thomas Blackthorne.  
  • The bumps on your tongue are called papillae. These papillae are covered with taste buds, which are collections of nerve-like cells that connect to nerves that transmit information about taste to your brain. We each have between 3,000 and 10,000 taste buds in our mouths.
  • The tongue is the most sensitive part of our body for touch. This high sensitivity allows us to test various aspects of food, such as shape and heat, and also protects us by magnifying unwanted objects, such as fish bones or small stones.
  • The tongue can move in all directions, up, down, sideways, and back and forth. It can also roll, curl, hollow, and make grooves. 
  • Contrary to what was once believed, the tongue senses sweet, salty, sour, bitter, and umami tastes all over its surface, not just in specific areas.
  • On average, men's tongues are longer than women's.

Fun Animal Tongue Facts:

  • A blue whale's tongue weighs as much as an adult elephant!
Blue whale's have the biggest tongues on the planet. (NOAA)

  • A chameleon's tongue can extend twice the length of its body and can move faster than the human eye can follow, hitting its target in about 30 thousandths of a second.
  • When a dog exercises, its tongue increases in size with greater blood flow and hangs out of its mouth. Moisture on the tongue along with panting help to cool the blood before it circulates back through the dog's body. 

The longest dog tongue belonged to a boxer
named Brandy. It was 17 inches long!
  • A cat's tongue has backwards-facing, hooked spines that help it comb its fur, removing dirt and parasites.
  • Hummingbirds have long, forked tongues covered in grooves. New high-speed photography shows exactly how this special tongue draws liquid into a hummingbird's mouth. See video here.

Hummingbirds have very specialized tongues that allow them to
sip nectar from deep flowers. (Dick Daniels)

  • An anteater's tongue is covered in sticky saliva while it feeds and can be flicked in and out of its mouth, entrapping ants and termites, up to 150 times a minute.

And, Finally, Something Really Gross

A "tongue-eating louse" that has replaced the
tongue of a sand steenbras fish.
A dastardly parasite called Cymothoa exigua, or the tongue-eating louse, enters its fish victims through the gills. Once inside the fish's mouth, the female attaches itself to the tongue, eventually removing so much blood from it that the tongue atrophies. "How horrible!" you might say. But it's not quite as bad a situation for the fish as it sounds. Once the tongue is gone, this little crustacean latches onto the muscles of the remaining stub and BECOMES THE FISH'S NEW TONGUE! In this position, the parasite lives out its life, feeding on blood from the fish or mucus.  
The tongue-eating louse, Cymothoa exigua, is the only known parasite that
acts as a working replacement for a host organ! (Frank Schulenburg)

References & Resources:

Edward Stanek IV, Steven Chang, Jun Takatoh, Bao-Xia Han, and Fan Wang. "Monosynaptic Premotor Circuit Tracing Reveals Neural Substrates for Oro-motor Coordination,"  eLife, June 3, 2014. DOI: 10.7554/eLife.02511

"Why tongue twisters are hard to say" - Nature.com

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